• It's time to cast your vote in the January 2025 Turning Challenge. (click here for details)
  • Conversations are now Direct Messages (click here for details)
  • Congratulations to Alan Weinberg for "Elm Burl Bowl" being selected as Turning of the Week for January 27, 2025 (click here for details)
  • Welcome new registering member. Your username must be your real First and Last name (for example: John Doe). "Screen names" and "handles" are not allowed and your registration will be deleted if you don't use your real name. Also, do not use all caps nor all lower case.

Raising grain discussion

Zach LaPerriere

Zach LaPerriere

Joined
Apr 1, 2015
Messages
603
Likes
449
Location
Sitka, Alaska, United States
Website
www.zachlaperriere.com
I've been doing some experiments with raising the grain while sanding and my conclusion is that I still have hard answers to what's best!

With the caveat that every species has different fiber lengths and characteristic (and I don't seem to turn many species in common with anyone else) I'll add what I've found:

1. It doesn't seem to matter if the bowl dries slowly after wetting or if I speed things up with a heat gun. *Footnote below*

2. Conventional wisdom is to sand to 240 or 320, wet the wood, dry it, then begin sanding at the same grit and work your way on up. So far in my experimenting it seems that raising the grain at 240 doesn't work any better than higher grains. I've had good results wetting the wood at 400 and then sand at 600 and call it done.

My other conclusion is that I don't really understand the fine points of wood behavior when raising the grain. I know that wood gets a little fuzzy when wetted if you don't raise the grain. I take on faith that's because stray fibers are left when sanding.

I'd love to understand this better. Has anyone seen a good discussion on the mechanics of raising the grain?



Footnote: I know a hair drier would be better, but my son installed the family hairdryer in his forge and I don't want it back with all that charcoal dust.
 
Zach.......I know that your history includes some experience with boat building, and maybe that is the background in why you feel it's necessary to "raise the grain" and continue sanding.....? Anyway, I don't get it......what is your purpose, or the benefits of wetting the bowl during the sanding?

ko
 
It depends on what finish your using. If I use a finish that doesn't have a water base I don't have to raise the grain. If I use a finish that does I do. The trick to raising grain is not to sand through what you just did. I will usually raise the grain on turnings after sanding to 220 or 400 and then I sand with the next higher grit when removing the little hairs. If you sand through what you just did as soon as you put the finish on it raises some more.
Another way of doing it is to apply the first coat of finish. that raises the grain but also stiffens the fibers. Now when you sand it lightly with a high grit your next coat of finish won't raise any more grain and you get a nice coat.
 
I don't sand wet wood.
I sand to finish. Then ( Depending whether the finish has water in it or not) I'll raise the grain and sand a little more after that dries to knock down the raised grain.

Mechanically this is what I think is happening
Sanding is a machining operation - - it cuts wood.
The fibers don't just happen to lie perfectly along the cut line they lay in other angles.
This means one end or another of the little tiny strips of wood are uncoupled from their mooring points on one end or the other so when wetted they swell up and are forced to stick up because the grains on either side are still fastened on either end. sanding chops off their little heads and cuts them down to size

Then finish doesn't raise the grain (at least no so dramatically)
 
odie said:
......what is your purpose, or the benefits of wetting the bowl during the sanding?
Click to expand...

Always a good question, Odie. I don't raise the grain with all of my bowls, I'm just doing some experiments. Here's why: I just don't find walnut oil to be a finish that preserves the smoothness once it's been washed a few times. The grain raises and becomes a little fuzzy, the finish a little dull. The degree to which this happens varies species to species.

When I raise the grain, the finish seems to stay closer to brand new...but often we don't see how a bowl really fares until it's been around for quite a while. In short, I'm just trying to see if I can make a better product. That said, I've never had someone come back to me with an issue on finish.
 
Raul McCai said:
I don't sand wet wood.
I sand to finish. Then ( Depending whether the finish has water in it or not) I'll raise the grain and sand a little more after that dries to knock down the raised grain.

Mechanically this is what I think is happening
Sanding is a machining operation - - it cuts wood.
The fibers don't just happen to lie perfectly along the cut line they lay in other angles.
This means one end or another of the little tiny strips of wood are uncoupled from their mooring points on one end or the other so when wetted they swell up and are forced to stick up because the grains on either side are still fastened on either end. sanding chops off their little heads and cuts them down to size

Then finish doesn't raise the grain (at least no so dramatically)
Click to expand...

I think your explanation is a good one, Raul. At least that's my understanding. Maybe I think too much, but I'd like to really know exactly what's going on. Too much time thinking while I'm sanding, apparently. ;)
 
Basically what Raul says. And I like John's regimen. My simple explanation would be that wetting the surface makes it swell slightly and that makes any broken fibers stick up. I don't often use a water based finish so I don't go through this grain raising exercise. There are exceptions where I don't care if the grain has been raised: when I apply something like Gesso or a metallic paint for patination in which case there's no need to raise the grain and then sand.

I just remembered a couple other instances where the grain would be raised -- bleaching the wood, whether using Oxalic acid to remove various stains or two-part hydrogen peroxide / sodium hydroxide to remove the natural pigments. Also, when using aniline dyes the grain is raised.
 
Bleaching raises the grain. Using water based stains or dyes raises the grain. I've already mentioned water based finishes. So it's good to know what to do just in case you use any of these products.
 
Zach LaPerriere said:
Always a good question, Odie. I don't raise the grain with all of my bowls, I'm just doing some experiments. Here's why: I just don't find walnut oil to be a finish that preserves the smoothness once it's been washed a few times. The grain raises and becomes a little fuzzy, the finish a little dull. The degree to which this happens varies species to species.

When I raise the grain, the finish seems to stay closer to brand new...but often we don't see how a bowl really fares until it's been around for quite a while. In short, I'm just trying to see if I can make a better product. That said, I've never had someone come back to me with an issue on finish.
Click to expand...

I've never found that raising the grain in wood finishing is necessary accept in the afore mentioned application of finishes, water based or otherwise. I am basing this on the fact that I have made and finished a fair amount of high quality woodwork and furniture over the years that still looks good. The bowls that are in frequent use and get a sink washing show some wear, but the grain isn't coming up.

It's interesting that you bring this up now Zach, because I just recently reapplied some walnut/carnauba oil to a bowl of yours that is in frequent use in my kitchen. It was not because the bowl was no longer smooth, it was just losing some luster that I wanted back, and, I wanted to add further protection.
 
Thanks, Tom. Your bowl is mountain ash, and I've found it to not really need raising the grain. Let me know how the carbauba holds up. I haven't found it fairs well with water, but it can always be reapplied. But then again I was applying carnauba to red alder and a few softwoods. I'm not sure if I ever buffed mountain ash with carnauba.

The main species that I see a possible need to raise the grain is red alder. In normal use, the grain doesn't raise, but in heavier use like a salad bowl that gets washed often, the grain raises a little despite the walnut oil. My guess is that if the walnut oil had been reapplied after several washings it wouldn't be an issue. Even then, it's just a small grain raising. I have well over a hundred alder bowls out there and no one has ever mentioned it...and I ask frequently. Still, I feel it: just a dullness in finish and slight furriness. The last thing I want to do is add a step, but it's really not much extra time, maybe a few minutes per bowl.
 
I've been finish turning some cottonwood. Mostly crotch wood, but I also took a few chunks from the butt, which was near 4' in diameter.

I didn't raise the grain on the crotch wood bowls, but when after oiling I could feel some raised grain. Hand sanding took care of it. So when it came time for the butt wood bowl, I wet the wood with a spray bottle and then took it inside by the woodstove to dry quickly.

Holy smokes... As the wood dried I could see individual fibers raising, many of them a little over 1/16 inch!

The first image is about as close as you can focus with an iphone, maybe 5 inches away. The second photo is zoomed in with iphone at the same distance.

IMG_1435.JPG IMG_1436.JPG
 
I think that bowl needs a shave. :)

I use DNA to raise the grain on highly figured maple before applying dye to the wood. It does just as well as water and evaporates much faster. I usually burn the fuzz off before the alcohol has completely evaporated, but it could also be sanded after the dye has dried.
 
i turned some cottonwood a few years ago, what a pain! The cottonwood in this region
has grain that runs in every direction..... a lot of work to get a good finish on a piece.
 
Very true, Mike. I thought of two comments on the forum recently, one where Odie said you tear fibers deeply when roughing heavy cuts, and the second where Bill said every cut is a finish cut. It took a good 1/4" of finish cuts to get through the tear out just from fairly clean roughing cuts.
One the positive side, the cottonwood I finished sands faster than anything else I ever sanded. And the crotch figure, as Gretch aptly pointed out, runs deep and far.
 
Hmm, I have never had an issue with the grain springing up after I sand and finish. I would guess that this may be because I soak most of my bowls in LDD (liquid dish washing detergent 1/2 water, 1/2 or less soap). This aids greatly in sanding. Maybe that raises the grain before I start to sand, but no real idea... I do try to sand in alternating scratch patterns when power sanding, maybe 99% of what I do, so use one edge of the pad for one grit, then the other side for the next one to make sure I get all the previous marks out. Think ( for one grit, and ) for the next....

robo hippy
 
I'm fairly convinced that grain raising is largely dependent on species. The worst I've had on any species until last week was a faint fuzziness. Cottonwood is an all level, 1/16" hairs.

Of the species I turn, I think grain raising is merited on alder, hemlock, and cottonwood. It seems more prevalent in softer species, and larger growth ring pieces.

I think you're right, Robo, on alternating scratch patterns. I don't always alternate between every grit, but I definitely think there's wisdom in alternating, especially at the last two or three grits..
 
I have proven that only us woodturners really care about the perfect finish. I took several pieces to a fair, lots were finished to 800, lots to 600, more to 320, I even left a few to 220. Did it make a difference? No... Nobody even noticed it or mentioned it... A gallery owner did ask why some pieces were finished to a higher gloss! As long as you dont have sanding marks, scratches, I tend to go up to just 320. Unless its a gallery or exhibition piece, then I will go to 800. I only have 800 because I found lots of boxes of 3 inch discs at half price at my local supplier a few years ago, I bought the entire stock of high grade Mirka stock, for half price...
I have also proven that the customer can't tell the difference between 320 or 400. When I couldn't cut the Koa end grain clean, many years ago, I experimented with lots of things to try to sand the torn grain, I remember mineral oil was a good one, but nothing beats a good sheer scrape and leaving the surface good enough to start sanding at 180, or the occasional 220.... Aloha
 
couldn't find another relevant discussion of grain raising than this on from 2 years ago, so let's see if someone's listening.. (Emiliano?)
I'm working on a hollow form of Honey Locust about 7 inches in diameter. This was a green log that I turned down and hollowed to about 3/16" thick. I had a hair dryer on it for 10 minutes outside and in and then sanded to 220 grit the other day and it felt very smooth. No finish was applied. I wrapped it with shrink wrap and left it overnight. Next day it looked good. no cracks so yesterday I worked on the finial lid. Late in the day I noticed that my smooth surface felt rough, like the grain had raised. So I sanded it again up through 400g. I left it unsealed last night and this morning it was still without cracks but the surface was rough again. This time I sanded to 320 and within a half an hour the surface was rough again! So, I surmise that the grain is raising, probably as the wood is still a little wet. The finial (different wood) lid is ready to fit to the opening later today.
The question is should I put the hair dryer on it again and for how long, OR reverse sand, OR put the finish on (I'll use wipe on poly) and not worry about the grain raising. Any other suggestions are appreciated.
 
Sounds to me like the escaping moisture from the wet wood is raising the grain.

If it were me, I'd probably set it aside for a few weeks to settle down, then re-sand. Repeat as necessary. And save the final fit on the lid till the body stops its antics.

Another option might be to hit the outside with sanding sealer and then sand that back. If it works, that'd raise the grain and seal it off. And force most of the drying to happen from the inside of the hollow form - not sure if that'd be good or bad.
 
2 things. It is probably still.wet. takes about a week or more to dry completely. You might also be sanding through the raised grain. You should sand just enough to knock off the fibers. .
 
It sounds like the wood still has bound water to lose even though it might not look and feel like it does. Using the hair dryer to dry the surface is causing various drying defects that explain what you have described. I think that Chapter 8 of the Forest Products Handbook is worth reading.

The short answer is put the hair dryer away. That is far too extreme for drying the wood. Let it sit on a shelf for approximately a month before doing the final turning.
 
I have done a few honey locust hollow forms.
A 3/16 thick form will dry in about 4 days. After it dries I sand it.

My drying room has a dehumidifier to keep it a 50% humidity.
My full process is to rinse the outside in the sink towel dry.
Put it in a box with the flaps closed for a day
Open a flap for a day, open all flaps for a day,
Put it in a shelf for a day or two. Then sand and finish it.

If the grain is raising it is still wet.
Be patient let it dry. With an even wall thickness of 3/16 it will dry in 4 days.
If you have thicker parts it will take longer.
 
davehu said:
couldn't find another relevant discussion of grain raising than this on from 2 years ago, so let's see if someone's listening.. (Emiliano?)
I'm working on a hollow form of Honey Locust about 7 inches in diameter. This was a green log that I turned down and hollowed to about 3/16" thick. I had a hair dryer on it for 10 minutes outside and in and then sanded to 220 grit the other day and it felt very smooth. No finish was applied. I wrapped it with shrink wrap and left it overnight. Next day it looked good. no cracks so yesterday I worked on the finial lid. Late in the day I noticed that my smooth surface felt rough, like the grain had raised. So I sanded it again up through 400g. I left it unsealed last night and this morning it was still without cracks but the surface was rough again. This time I sanded to 320 and within a half an hour the surface was rough again! So, I surmise that the grain is raising, probably as the wood is still a little wet. The finial (different wood) lid is ready to fit to the opening later today.
The question is should I put the hair dryer on it again and for how long, OR reverse sand, OR put the finish on (I'll use wipe on poly) and not worry about the grain raising. Any other suggestions are appreciated.
Click to expand...
Not to put any of us great woodturners down, but... I have noticed that our fellow flat woodworkers usually know a lot more about finishing than us mere woodturners... I would also guess that you have some moisture in that piece. Other than that, lots of humidity could also do it. I'm talking about a hot humid day in Hawaii or Florida... I have a homemade kiln, a broken down flower Lei dispenser, looks like a tall skinny refrigerator, the ones you see at supermarkets with drinks. The best thing about it is the glass door, I dont have to open it to see the humidity or what's going on in there. I keep all my photo equipment in 2 dehumidifier cabinets. Just opening the door to get a camera out, makes the humidity go up from 35 to 48...
 
My shop is air conditioned and the humidity is 59%. It's been 2 1/2 days already so I'll give it through the weekend and try again. Although retirement has allowed me to be much more patient than I used to be... it appears I still have a way's to go! Thanks to all for the advice. I'll let you know how it goes.
 
Bill Boehme said:
It sounds like the wood still has bound water to lose even though it might not look and feel like it does. Using the hair dryer to dry the surface is causing various drying defects that explain what you have described. I think that Chapter 8 of the Forest Products Handbook is worth reading.

The short answer is put the hair dryer away. That is far too extreme for drying the wood. Let it sit on a shelf for approximately a month before doing the final turning.
Click to expand...
Thanks Bill. some interesting stuff in there.
 
The advantage of having hundreds of unfinished wood turned projects sitting on the shelf drying, you never run out of items you can work on.
 
Zach, I did not read all the replies, so maybe it was covered already.
I do sand my wood to the final grids, anywhere from 320 to whatever I feel like.
After that I coat with Polymerized Tung Oil, I let that harden, any fibers that are raised will be saturated with the Tung oil and be hard, they get easily sanded off, and then I will add the next coat of Tung oil finish over that, I never have any raising of the wood fibers after the first coat, works for me.
 
You must log in or register to reply here.
Back
Top